I have been fighting automated comment spam robots (see also refererblock update, and hit counter changes) with my modified writeback plugin that uses a blacklist of spam words and URLs. However, I'm getting tired of updating the blacklist and removing spam comments that get through the filter. So I decided to install the wbcaptcha plugin written by Pasi Savolainen. His plugin uses the FIGlet program to generate an ASCII "image" of random letters:
_
___ _ __ | |__ __ _
/ _ \| '_ \ | '_ \ / _` |
| __/| | | || | | || (_| |
\___||_| |_||_| |_| \__,_|
A person leaving a comment then enters the letters (enha for the image above) as a "key" along with their comments. The plugin then validates that the key matches the generated image before it allows the comment to be posted. This is similar to the approach used by other blog software to distinguish humans from automated spam programs.
Pasi's plugin worked by executing figlet in a subshell whenever someone wanted to post a comment. I wanted to change this approach since I don't have the ability to install figlet on my web host and I didn't want to pay the performance cost of calling a program through the shell.
So I found the Text::FIGlet Perl package on CPAN and made a few small edits to Pasi's plugin to allow it to invoke the FIGlet Perl code without the shell. This simplified the plugin and sped up it's performance. I've sent my changes to Pasi in case he wants to incorporate them in a future release of his plugin.
I've decided to leave my blacklist in place, since I'm sure I'll still be facing human comment spammers looking to promote their websites. The last change I can think to make to further discourage spammers will be to change all <a> elements in comments to include the rel="nofollow" attribute supported by most portal/search websites.
I also took this opportunity to add some name anchors to my foot.htm and foot.html files so clicking on the "Comments" link on my index pages now takes you directly to the comments section of the individual article. Similarly, selecting "Add Your Comment" and Posting a comment also show the writeback for and the last added comment respectively. This makes for less scrolling on long articles and multiple comments.
Unfortunately, I don't think this will actually reduce the spammer hits on my site since these are due to automated "bots". I doubt the spammers actually check if their comments get posted, they are just hoping for a comment to "get through" occaisionally so their sites can can get some "Google Juice". So they'll keep pounding on my site although hopefully fewer spam comments will get through.
Please email me at the address shown in the right hand menu bar if you have any problems posting comments.